Availability

mission capable rateavailablemission capablemission-capable rateAvailability (Reliability Engineering)Mission-Capableoperational availabilityoperational readinessPartially mission capablesystem readiness
In reliability theory and reliability engineering, the term availability has the following meanings:wikipedia
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High availability

high-availabilityavailabilityfive nines
In high availability applications, a metric known as nines, corresponding to the number of nines following the decimal point, is used.
Availability refers to the ability of the user community to obtain a service or good, access the system, whether to submit new work, update or alter existing work, or collect the results of previous work.

Reliability engineering

reliabilityreliability theoryreliable
In reliability theory and reliability engineering, the term availability has the following meanings:
Reliability is closely related to availability, which is typically described as the ability of a component or system to function at a specified moment or interval of time.

Downtime

network outageoutagescheduled downtime
Availability measures are classified by either the time interval of interest or the mechanisms for the system downtime.
Reliability, availability, recovery, and unavailability are related concepts.

Mean time to repair

MTTR
1. The impact of a repairable-element (refurbishing/remanufacture isn't repair, but rather replacement) on the availability of the system, in which it operates, equals mean time between failures MTBF/(MTBF+ mean time to repair MTTR).
MTTR is often part of a maintenance contract, where a system whose MTTR is 24 hours is generally more valuable than for one of 7 days if mean time between failures is equal, because its Operational Availability is higher.

Lockheed Martin F-22 Raptor

F-22 RaptorF-22F-22A Raptor
Effectively maintaining the stealth features can decrease the F-22's mission capable rate to 62–70%.

Optimal maintenance

Availability is well established in the literature of stochastic modeling and optimal maintenance.
Cost functions depending on the reliability, availability and maintainability characteristics of the system of interest determine the parameters to minimize.

Spare part

sparepartsPart
Availability considered in maintenance modeling can be found in Barlow and Proschan [1975] for replacement models, Fawzi and Hawkes [1991] for an R-out-of-N system with spares and repairs, Fawzi and Hawkes [1990] for a series system with replacement and repair, Iyer [1992] for imperfect repair models, Murdock [1995] for age replacement preventive maintenance models, Nachlas [1998, 1989] for preventive maintenance models, and Wang and Pham [1996] for imperfect maintenance models.
As a result, operational availability is impaired.

Systems engineering

systems engineersystem engineeringsystems
Refer to Systems engineering for more details

Generating Availability Data System

Generating Availability Data System (Electricity Industry)
For example, the North American Electric Reliability Corporation implemented the Generating Availability Data System in 1982.
*Availability

Decimal

base 10decimal systemdecimal fraction
However, typical availability values are specified in decimal (such as 0.9998).

Predictive maintenance

predictivemaintain
The maintenance strategy can influence the reliability of a system (e.g. by preventive and/or predictive maintenance), although it can never bring it above the inherent reliability.

Fault tree analysis

fault treeevent treesfault tree analysis (FTA)
Fault tree analysis and related software are developed to calculate (analytic or by simulation) availability of a system or a functional failure condition within a system including many factors like:

Mean time between failures

MTBFmean time between failuremean time to failure
1. The impact of a repairable-element (refurbishing/remanufacture isn't repair, but rather replacement) on the availability of the system, in which it operates, equals mean time between failures MTBF/(MTBF+ mean time to repair MTTR).

Stochastic modelling (insurance)

stochastic modelingstochastic modelling
Availability is well established in the literature of stochastic modeling and optimal maintenance.

Power station

power plantpower plantspower stations
Availability is used extensively in power plant engineering.

North American Electric Reliability Corporation

NERCNorth American Electric Reliability Corporation (NERC)North American
For example, the North American Electric Reliability Corporation implemented the Generating Availability Data System in 1982.